During the period from 04/01/79 to 03/31/80 studies will be performed to reach the two major objectives of the research project: 1) to obtain data about the neural and hormonal control of hunger and satiety, and 2) to gain information about the neurophysiological mechanisms of pain. Studies related to the first objective will examine the influence of the nucleus ventromedialis hypothalami (nVmH) on the release of thyroxine. Studies related to the second objective will attempt to localize the pathways involved in electroanalgesia induced by stimulation of the periaqueductal gray matter (PAG). All experiments will be performed on animals (cats, rats) given an adequate dose of alpha-chloralose and urethane. The circulating thyroxine levels will be determined before and after electrical stimulation of the nVmH, and these values will be compared to the thyroxine levels in control animals with lesioned nVmH. In experiments dealing with the pathways for electroanalgesia the role of the spinocervical pathway and the dorsal column fiber system in mediating such an analgesia will be studied by electrophysiological methods described in Brain Research 103: 425, 1976. It is expected that these studies will provide data concerning 1) the hypothalamic control of food utilization and 2) the neural mechanisms of electroanalgesia.